Reaction method for reacting reaction object with liquid containing the reaction object being in contact with granular porous body

ABSTRACT

The present invention provides efficient reaction conditions by clarifying a relationship between a contact time and an optimum particle diameter etc. in a method for reacting a reaction object with a liquid containing the reaction object being in contact with a granular porous body. The upper limit D (mm) of the particle diameter of the granular porous body is determined from D=0.556×LN (T)+0.166 in a column flow method in non-circulation type, and determined from D=0.0315×T+0.470 in the column flow method in a circulation type and a shaking method. The contact time T (seconds) is given by a value obtained by dividing the volume (m 3 ) of the granular porous body by the flow rate (m 3 /second) of the liquid in the column flow method in non-circulation type, given by a value obtained by multiplying the fluid flow time (seconds) of the liquid by a volume ratio obtained by dividing the volume of the granular porous body by the volume of the liquid in the column flow method in a circulation type, and given by a value obtained by multiplying the volume ratio by the elapsed time (seconds) after addition of the granular porous body in the liquid in the shaking method.

TECHNICAL FIELD

The present invention relates to a granular porous body which includes askeleton body including an inorganic compound having a three-dimensionalcontinuous network structure, and which has a two-step hierarchicalporous structure including through-holes formed in voids in the skeletonbody, and pores extending from a surface to the inside of the skeletonbody and dispersively formed on the surface. Particularly, the presentinvention relates to a reaction method for reacting a reaction objectwith a liquid containing the reaction object such as a metal ion and alow-molecular-weight compound being in contact with the granular porousbody.

BACKGROUND ART

A monolith porous body including an inorganic compound having a two-stephierarchical porous structure is a reactive porous body which includes ablock-like skeleton body including an inorganic compound having athree-dimensional continuous network structure, and which is excellentin mass transfer from a hydrodynamic point of view owing tomicrometer-order through-holes formed in voids in the skeleton body andhaving a characteristic three-dimensional continuous network structureand nanometer-order pores existing in the skeleton body. For example, asan example of separating and regenerating antibody molecules, there hasbeen a case where the contact time is optimized and shortened to about 2seconds (see Patent Document 1 below).

However, for fully reacting a fluid by causing the fluid to pass througha monolithic porous body of a block body, a dedicated jacket that coversthe monolithic porous body without a gap is required. When a gap isgenerated between a monolithic porous body with through-holes having asize in a range of 0.1 to 100 μm and a jacket, a fluid is leaked throughthe gap, and therefore, it is necessary to control the gap inseveral-micron unit for causing the fluid to fully pass through theinside of the monolith porous body.

Thus, a porous body can be used with the porous body merely filled in acolumn provided beforehand when the porous body is a granular porousbody having a two-step hierarchical porous structure in whichthrough-holes and pores exist in particles obtained by crushing amonolithic porous body. As one example, it has been suggested that acolumn container is filled with a granular inorganic filler obtained bygrinding the above-mentioned monolithic porous body, and applied as apretreatment column for analysis (see Patent Document 2 below).

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Unexamined Patent Publication No.    2014-2008-   Patent Document 2: Japanese Unexamined Patent Application    Publication No. 2006-192420

Non-Patent Document

-   Non-Patent Document 1: Fred E. Regnier, “Perfusion Chromatography”,    Nature, 350, pp. 634-635 (18 Apr. 1991)

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Unlike single-pore mesoporous particles in which only pores are presentin particles, a granular porous body having a two-step hierarchicalporous structure has through-holes serving as diffusion channels inparticles. Thus, it is considered that a fluid is easily quicklydiffused to the inside of the particle, and good reaction efficiency isobtained even when the particle diameter is larger as compared to asingle-pore particle. However, individual specific studies on thephysical properties of the granular porous body have not beensufficiently conducted, and an optimum particle diameter and clearreaction conditions such as a contact time in a method for reacting areactant with a fluid containing the reactant being in contact with thegranular porous body have not been found. There are many methods forreacting a monolithic porous body, but an optimum method for reacting aninorganic porous body having a two-step hierarchical porous structure isunclear, and has not been heretofore standardized.

As a diffusion behavior of molecules in a solution in particles,molecules are diffused very slowly through numerous nanometer-scalepores present in particles in the case of conventional one-stepsingle-pore particles. In molecular diffusion, the diffusion rate variesdepending on the strength of interaction with the pore surfaces ofparticles, but as compared to a micrometer region where dispersion andconvection of molecules can be controlled, molecular diffusion is slowerby a factor of 1000 or more.

For example, in the case of silica gel, there exist particles having aparticle diameter of several microns to several millimeters as theabove-mentioned single-pore particles. Particles which are commonly usedin chromatography etc. in which the particles are used with a relativelyshort contact time of several seconds to several minutes have a particlediameter of about 5 to 200 μm. In addition, particles which are commonlyused in adsorption of water or a low-molecular-weight compound, etc. inwhich the particles are used with a relatively long contact time ofseveral hours to several days have a particle diameter of about 0.3 to 2mm. As described above, it takes a considerable time for moleculardiffusion to a deep part of the particle, and therefore it is necessaryto reduce the particle diameter to a micrometer when a treatment with ashort contact time of minutes or less is required.

On the other hand, it is known that in the case of a granular porousbody having a two-step hierarchical porous structure in whichmicrometer-order through-holes are continuously exist in particles, asolution is efficiently dispersed and convected in the particles due toexistence of micrometer-order through-holes, and therefore the solutionis quickly diffused to a deep part of the particle (see, for example,Non-Patent Document 1). This phenomenon is called perfusion.

A reaction method with a fluid containing a reaction object being incontact with a granular porous body is inferior in reaction efficiencyto a method with the fluid passing directly through a monolithic porousbody. However, the monolithic porous body has a through-hole diameter ofabout 100 μm at most, and depending on the viscosity and flow volume ofa fluid, the column pressure increases, so that the fluid is loaded, andtherefore a high-speed treatment is possible, but there is a certainlimit. On the other hand, in the case of a granular porous body, a fluidflows through a gap in the granular porous bodies, and therefore byincreasing the particle diameter, the gap can be expanded toconsiderably reduce channel resistance.

However, as the particle diameter increases, the diffusion distance inthe particle becomes longer, and therefore even if through-holes exist,consequently an enormous amount of time is required for the molecule toreach a deep part of the particle when the particle diameter increasesto several millimeters. This is because even if the convection in thethrough-hole is fast, there is a difference between the convection speedin the particle and the convection speed at the particle surface in thecase of an extremely large particle diameter for which the convectionspeed is higher by a factor of 10 or more when the fluid is quicklydispersed on the particle surface.

From the above, a relationship between a contact time and an optimumparticle diameter, a through-hole diameter, a pore diameter and the likein a method for reacting a reactant with a fluid containing the reactantbeing in contact with a granular porous body having a two-stephierarchical porous structure has not been clarified yet.

The present invention has been made in in view of the problems of thegranular porous body having a two-step hierarchical porous structure,and an object of the present invention is to provide efficient reactionconditions by clarifying a relationship between a contact time and anoptimum particle diameter etc. in a method for reacting a reactionobject with a liquid containing the reaction object being in contactwith the granular porous body.

Means for Solving the Problem

The inventors of the present application have found that when thereaction method includes a circulation-type or non-circulation-typecolumn flow method in which the liquid is caused to pass through acolumn filled with a granular porous body, so that the liquid isdiffused in the granular porous body, or a shaking method in which agranular porous body is dispersively added in the liquid, and the liquidand the granular porous body are shaken to diffuse the liquid in thegranular porous body, a particle diameter ensuring certain reactionefficiency is given by a natural logarithm of a contact time between theliquid and the granular porous body regardless of the molecular size ofa reaction object in the non-circulation-type column flow method, and aparticle diameter ensuring certain reaction efficiency is given by alinear function of the contact time regardless of the molecular size ofthe reaction object in the circulation-type column flow method and theshaking method, and the inventors have confirmed the effectiveness andviability of the findings on the basis of specific experiments.

That is, for achieving the above-mentioned object, a first aspect of thepresent invention provides a reaction method for reacting a reactionobject with a liquid containing the reaction object being in contactwith a granular porous body,

wherein

the reaction object is a metal ion, or a low-molecular-weight compoundhaving a molecular weight of 2000 or less,

the method includes a column flow method in which the liquid is causedto pass through a column filled with the granular porous body, so thatthe liquid is diffused in the granular porous body, or a shaking methodin which the granular porous body is dispersively added in the liquid,and the liquid and the granular porous body are shaken to diffuse theliquid in the granular porous body,

the granular porous body includes a skeleton body including an inorganiccompound having a three-dimensional continuous network structure, andhas a two-step hierarchical porous structure including through-holesformed in voids in the skeleton body, and pores extending from a surfaceto an inside of the skeleton body and dispersively formed on thesurface,

a most frequent pore diameter in a pore diameter distribution of thepores is within a range of 2 nm or more and 20 nm or less when thereaction object is a metal ion, and the most frequent pore diameter ofthe pores is within a range of 5 nm or more and 50 nm or less when thereaction object is the low-molecular-weight compound,

a most frequent pore diameter in a pore diameter distribution of thethrough-holes is equal to or more than 5 times of the most frequent porediameter of the pores, and within a range of 0.1 μm or more and 50 μm orless,

a particle diameter of the granular porous body is equal to or more than2 times of the most frequent pore diameter of the through-holes, andwithin a range of 20 μm or more and not more than an upper limit D (mm)defined depending on a contact time T (seconds) between the liquid andthe granular porous body,

the upper limit D is given by:

D=0.556×LN(T)+0.166

where the function LN is a natural logarithm in a case of the columnflow method in a non-circulation type in which the liquid is caused tocontinuously pass through the column while a concentration of thereaction object in the liquid is kept constant; or

D=0.0315×T+0.470

in a case of the column flow method in a circulation type, in which theliquid after the reaction is returned to the column, and continuouslycirculated, and the shaking method, and

the contact time T (seconds) is given by:

a value obtained by dividing a volume (m³) of the granular porous bodyby a flow rate (m³/second) of the liquid in the case of the column flowmethod in a non-circulation type;

a value obtained by multiplying a fluid flow time (seconds) of theliquid by a volume ratio obtained by dividing the volume of the granularporous body by a volume of the liquid in the case of the column flowmethod in a circulation type; or

a value obtained by multiplying the volume ratio by an elapsed time(seconds) after addition of the granular porous body in the liquid inthe case of the shaking method.

The volume of the granular porous body is a volume as measured with thegranular porous body densely filled into a predetermined container, andincludes a volume of a solid part of the skeleton body, a volume ofspaces occupied by through-holes and pores, and a volume of air gapsbetween particles.

Further, it is preferable that in the reaction method according to thefirst aspect, the reaction object is a metal ion, and a functional grouphaving affinity with the metal ion is chemically modified on a surfaceof the granular porous body.

Further, it is preferable that in the reaction method of the firstaspect, the metal ion is adsorbed to the surface of the granular porousbody by undergoing a complexation reaction with the functional group.

Further, for achieving the above-mentioned object, a second aspect ofthe present invention provides a reaction method for reacting a reactionobject with a liquid containing the reaction object being in contactwith a granular porous body,

wherein

the reaction object is a compound having a molecular weight of 2000 ormore and 1000000 or less,

the method includes a non-circulation-type column flow method in whichwhile a concentration of the reaction object in the liquid is keptconstant, the liquid is caused to continuously pass through a columnfilled with the granular porous body, so that the liquid is diffused inthe granular porous body,

the granular porous body includes a skeleton body including an inorganiccompound having a three-dimensional continuous network structure, andhas a two-step hierarchical porous structure including through-holesformed in voids in the skeleton body, and pores extending from a surfaceto an inside of the skeleton body and dispersively formed on thesurface,

a most frequent pore diameter in a pore diameter distribution of thepores is within a range of 10 nm or more and 100 nm or less,

a most frequent pore diameter in a pore diameter distribution of thethrough-holes is equal to or more than 5 times of the most frequent porediameter of the pores, and within a range of 0.1 μm or more and 50 μm orless,

a particle diameter of the granular porous body is equal to or more than2 times of the most frequent pore diameter of the through-holes, andwithin a range of 20 μm or more and not more than an upper limit D (mm)defined depending on a contact time T (seconds) between the liquid andthe granular porous body,

the upper limit D is given by:

D=0.198×LN(T)+0.270

where the function LN is a natural logarithm, and

the contact time T is given by a value obtained by dividing a volume(m³) of the granular porous body by a flow rate (m³/second) of theliquid.

Further, it is preferable that in the reaction method according to thesecond aspect, a functional group having affinity with the reactionobject is chemically modified on a surface of the granular porous body.

Further, it is preferable that in the reaction method according to thefirst or second aspect, the granular porous body is obtained by grindingand granulating a massive porous body prepared by a sol-gel method,

the massive porous body includes a skeleton body including the inorganiccompound having a three-dimensional continuous network structure, andhas a two-step hierarchical porous structure including through-holesformed in voids in the skeleton body, and pores extending from a surfaceto an inside of the skeleton body and dispersively formed on thesurface, a most frequent pore diameter in a pore diameter distributionof the pores of the massive porous body is within a range identical tothe range of the most frequent pore diameter in the pore diameterdistribution of the pores of the granular porous body, and a mostfrequent pore diameter in a pore diameter distribution of thethrough-holes of the massive porous body is within a range identical tothe range of the most frequent pore diameter in the pore diameterdistribution of the through-holes of the granular porous body.

Further, in the reaction method of the first or second aspect, theinorganic compound is preferably silica or titania.

Further, the present invention provides a granular porous body used forreaction with a metal ion,

wherein

the granular porous body includes a skeleton body including an inorganiccompound having a three-dimensional continuous network structure, andhas a two-step hierarchical porous structure including through-holesformed in voids in the skeleton body, and pores extending from a surfaceto an inside of the skeleton body and dispersively formed on thesurface,

a most frequent pore diameter in a pore diameter distribution of thepores is within a range of 2 nm or more and 20 nm or less,

a most frequent pore diameter in a pore diameter distribution of thethrough-holes is equal to or more than 5 times of the most frequent porediameter of the pores, and within a range of 0.1 μm or more and 50 μm orless,

a particle diameter of the granular porous body is equal to or more than2 times of the most frequent pore diameter of the through-holes, andwithin a range of 20 μm or more and 4 mm or less, and

a functional group having affinity with the metal ion is chemicallymodified on a surface of the granular porous body.

Further, it is preferable that the granular porous body according to theaforementioned aspect has a function in which the functional groupadsorbs the metal ion to the surface of the granular porous body byundergoing a complexation reaction with the metal ion.

Further, it is preferable that the granular porous body according to theaforementioned aspect is obtained by grinding and granulating a massiveporous body prepared by a sol-gel method, the massive porous bodyincludes a skeleton body including the inorganic compound having athree-dimensional continuous network structure, and has a two-stephierarchical porous structure including through-holes formed in voids inthe skeleton body, and pores extending from a surface to an inside ofthe skeleton body and dispersively formed on the surface, a mostfrequent pore diameter in a pore diameter distribution of the pores ofthe massive porous body is within a range identical to the range of themost frequent pore diameter in the pore diameter distribution of thepores of the granular porous body, and a most frequent pore diameter ina pore diameter distribution of the through-holes of the massive porousbody is within a range identical to the range of the most frequent porediameter in the pore diameter distribution of the through-holes of thegranular porous body.

Further, in the granular porous body according to the aforementionedaspect, the inorganic compound is preferably silica or titania.

Further, the present invention provides a column used for reaction witha metal ion, wherein a column container is filled with the granularporous body according to the aforementioned aspect.

Further, it is preferable that in the column according to theaforementioned aspect, a particle diameter of the granular porous bodyis not more than an upper limit D (mm) determined depending on a contacttime T (seconds) between a liquid containing the metal ion and thegranular porous body,

the upper limit D is given by:

D=0.556×LN(T)+0.166

where the function LN is a natural logarithm, and

the contact time T is given by a value obtained by dividing a volume(m³) of the granular porous body by a flow rate (m³/second) of theliquid, in a case where passage of the liquid is non-circulation-typepassage, and

the upper limit D is given by:

D=0.0315×T+0.470,

the contact time T is given by a value obtained by multiplying a fluidflow time (seconds) of the liquid by a volume ratio obtained by dividingthe volume of the granular porous body by a volume of the liquid, in acase where passage of the liquid is circulation-type passage.

Effects of the Invention

According to the reaction method of the aforementioned aspect, anoptimum particle diameter range of the granular porous body isdetermined depending on which of a non-circulation-type column flowmethod, a circulation-type column flow method and a shaking method isused as a method for diffusing a reaction object-containing liquid inthe granular porous body and bringing into contact with the liquid withthe granular porous body (hereinafter, referred to as “contact method”),and a contact time between the liquid and the granular porous body inthe contact method, and therefore use of a granular porous body whichhas a particle diameter within an unnecessarily small range, and whichflies so easily that care is needed for handling can be avoided.

In addition, since a particle diameter range of the granular porous bodyis determined by the same relational expression for the metal ion andthe low-molecular-weight compound, the particle diameter range of thegranular porous body which is established for one kind of reactionobject can be extended and applied to another kind of reaction object.In addition, for reactions with different contact times, the samerelational expression can be used to set a particle diameter range, andthus labor for conducting many preliminary experiments can be saved.

Further, since substantially the same relational expression can be usedfor the circulation-type column flow method and the shaking method, theparticle diameter range of the granular porous body which is establishedin one of the circulation-type column flow method and the shaking methodcan be extended and applied to the other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically and two-dimensionally showing astructural feature of a granular porous body according to the presentinvention.

FIG. 2 is a view showing an example of a pore diameter distribution ofthrough-holes and pores of the granular porous body according to thepresent invention.

FIG. 3 is a SEM photograph showing an example of a three-dimensionalcontinuous network structure of a silica monolith porous body.

FIGS. 4(A) and 4(B) are views showing a change in concentration ratio ofa post-reaction concentration and an initial concentration in Example 1and a comparative example.

FIGS. 5(A) to 5(G) are views showing a change in concentration ratio ofa post-reaction concentration and an initial concentration in Examples 1to 7 for different solution flow rates where the reaction object is acopper ion.

FIGS. 6(A) to 6(E) are views showing a change in concentration ratio ofa post-reaction concentration and an initial concentration in Examples 8to 12 for different solution flow rates where the reaction object is apalladium ion.

FIGS. 7(A) to 7(D) are views showing a change in concentration ratio ofa post-reaction concentration and an initial concentration in Examples13 to 16 for different solution flow rates where the reaction object isa blue pigment.

FIGS. 8(A) to 8(D) are views showing a change in concentration ratio ofa post-reaction concentration and an initial concentration in Examples17 to 20 for different solution flow rates where the reaction object isa brown sugar.

FIGS. 9(A) to 9(E) are views each showing an upper limit D1 in anon-circulation-type column flow method, which is derived for eachreaction object, a corresponding contact time T, and a relationalexpression thereof in a semi-logarithmic graph.

FIG. 10 is a view collectively showing the upper limits D1, thecorresponding contact times T and the relational expressions shown inFIGS. 9(B) to 9(D) in a semi-logarithmic graph.

FIG. 11 is a view showing a change in concentration ratio of apost-reaction concentration and an initial concentration in Example 21for different pore diameters where the reaction object is a copper ion.

FIGS. 12(A) to 12(C) are views showing a change in concentration ratioof a post-reaction concentration and an initial concentration inExamples 22 to 24 for different through-hole diameters or pore diameterswhere the reaction object is a copper ion.

FIGS. 13(A) and 13(B) are list tables showing particle diameter ranges,combinations of the through-hole diameter and the pore diameter, andresults of measuring a misfetch ratio for each elapsed time in ExampleA.

FIG. 14 is a list table showing particle diameter ranges, and results ofmeasuring a leakage ratio for each elapsed time in Example B with adifferent functional group.

FIG. 15 shows particle diameter ranges, and results of measuring aleakage ratio for each elapsed time in Example C with a different metalion.

FIG. 16 is a view showing an upper limit D1 in a shaking method and acirculation-type column flow method, a corresponding contact time T, anda relational expression thereof in a double logarithmic graph.

FIG. 17 is a view showing results of a concentration ratio of apost-reaction concentration and an initial concentration for eachelapsed time in a circulation-type column flow method.

DESCRIPTION OF EMBODIMENTS

An embodiment of a reaction method according to the present invention(hereinafter, referred to as “this reaction method” as necessary), agranular porous body used in this reaction method (hereinafter, simplyreferred to as a “granular porous body”), and a column formed by fillinga column container with the granular porous body and used in thisreaction method (hereinafter, referred to as “this column” as necessary)will be described with reference to the drawings.

First, a structural feature of a granular porous body 1 to be used inthis reaction method will be described. As schematically andtwo-dimensionally shown in FIG. 1, each particle of the granular porousbody 1 includes a skeleton body 2 including an inorganic compound havinga three-dimensional continuous network structure, and has a two-stephierarchical porous structure including through-holes 3 formed in voidsin the skeleton body 2, and pores 4 extending from a surface to theinside of the skeleton body 2 and dispersively formed on the surface. Inthis specification, the “surface of the skeleton body” refers to asurface of the skeleton body exposed toward the through-hole, and doesnot include the inner wall surface of the pore formed in the skeletonbody. In addition, the total surface of the skeleton body with the“surface of the skeleton body” added to the inner wall surface of thepore is referred to as a “surface of the granular porous body”. Thethrough-hole and the pore may also be referred to as a macropore and amesopore, respectively.

In this embodiment, the inorganic compound that forms the skeleton body2 is assumed to be silica gel or silica glass (SiO₂). In each particleof the granular porous body 1, the optimum range of the most frequentpore diameter ϕ0 m in the pore diameter distribution of pores 4 variesdepending on a reaction object of this reaction method as describedlater, but generally falls within a range of 2 nm or more and 100 nm orless, the most frequent pore diameter ϕ1 m in the pore diameterdistribution of through-holes 3 is equal to or more than 5 times of themost frequent pore diameter ϕ0 m of pores 4, and within a range of 0.1μm or more and 50 μm or less, and the particle diameter Dp is equal toor more than 2 times of the most frequent pore diameter ϕ1 m ofthrough-holes 3, and generally within a range of 20 μm or more and 4 mmor less. However, as described later, the upper limit D1 of the particlediameter Dp is further limited depending on the size of the reactionobject, the method for bringing the granular porous body 1 into contactwith a reaction object-containing liquid used in this reaction method,and the contact time.

Each of the most frequent pore diameters of through-holes 3 and pores 4is a most frequent value (mode value) in a pore diameter distribution asmeasured by a well-known mercury press-in method. As the pore diameterdistribution of pores 4, one derived by a well-known BJH method based onnitrogen adsorption measurement may be used. In addition, the mostfrequent pore diameter of through-holes 3 is not much different from anaverage pore diameter derived as an average of through-hole diametersmeasured at 20 to 30 arbitrary dispersed points in an electronmicrograph of the skeleton body 2. FIG. 2 shows an example of porediameter distributions of through-holes 3 and pores 4 as measured by amercury press-in method. The abscissa represents the pore diameters(unit: μm) of through-holes 3 and pores 4, and the ordinate represents adifferential pore volume (unit: cm³/g). However, the differential porevolume also includes the differential through-hole volume. The peak onthe left side shows the most frequent pore diameter of pores 4, and thepeak on the right side shows the most frequent pore diameter ofthrough-holes 3. In the example in FIG. 2, the most frequent porediameters of through-holes 3 and pores 4 are about 1.77 μm and about 17nm, respectively, the half-widths of through-holes 3 and pores 4 areabout 0.34 μm and about 3.4 nm, respectively. The results of measuringthe pore diameter distributions of through-holes 3 and pores 4 for thegranular porous body 1 having a granular shape are substantiallyidentical to the results of measuring the pore diameter distributions ofthrough-holes 3 and pores 4 for a monolithic porous body (equivalent toa massive porous body) having the same two-step hierarchical porousstructure before granulation as described later. Therefore, the porediameter distributions of through-holes 3 and pores 4 may be measured inthe state of a monolithic porous body.

In this embodiment, the granular porous body 1 is prepared in thefollowing manner: a silica monolithic porous body which is synthesizedby a spinodal decomposition sol-gel method as described in detail belowand which includes silica gel or silica glass having a massivethree-dimensional continuous network structure is ground to begranulated before or after sintering. FIG. 3 shows an example of a SEM(scanning electron microscope) photograph showing the three-dimensionalcontinuous network structure of the silica monolithic porous body. Sinceparticles having a large particle diameter and particles having a smallparticle diameter coexist in the granular porous body 1 just aftergrinding, the particles are sieved and classified to obtain the granularporous body 1 having a particle diameter in a desired range. Therefore,the upper limit and the lower limit of the particle diameter range arethe values of the apertures of two kinds of sieves that are used in theclassification treatment.

Next, a method for preparing the granular porous body 1 will bedescribed. The method for preparing the granular porous body 1 isbroadly divided into a step of synthesizing a monolithic porous bodyhaving a two-step hierarchical porous structure as a raw material of thegranular porous body 1, and a subsequent granulation step.

First, the step of synthesizing a monolithic porous body includingsilica gel or silica glass having a three-dimensional continuous networkstructure by a spinodal decomposition sol-gel method will be described.The synthesis step is further divided into a sol preparation step, agelation step and a removal step.

In the sol preparation step, a silica precursor as a raw material ofsilica gel or silica glass, and a coexisting substance serving to inducesol-gel transition and phase separation in parallel are added in an acidor alkaline aqueous solution, and at a low temperature of, for example,5° C. or lower at which sol-gel transition hardly proceeds, the mixtureis stirred to cause a hydrolysis reaction, so that a uniform precursorsol is prepared.

As a main component of the silica precursor, water glass (sodiumsilicate aqueous solution), or an inorganic or organic silane compoundcan be used. Examples of the inorganic silane compound includetetra-alkoxysilanes such as tetramethoxysilane, tetraethoxysilane,tetra-isopropoxysilane, tetra-n-butoxysilane and tetra-t-butoxysilane.Examples of the organic silane compound include trialkoxysilanes such astrimethoxysilane, triethoxysilane, triisopropoxysilane and triphenoxysilane, dialkoxysilanes such as methyldiethoxysilane,methyldimethoxysilane, ethyldiethoxysilane and ethyldimethoxysilane,monoalkoxysilanes such as dimethylethoxysilane anddimethylmethoxysilane, and the like, each of which has a substituentsuch as methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, hexadecyl,octadecyl, dodecyl, phenyl, vinyl, hydroxyl, ether, epoxy, aldehyde,carboxyl, ester, thionyl, thio and amino. Alkoxysilicates containing acrosslinking reaction rate controlling group substituent such as amonoalkyl, a dialkyl and a phenyltriethoxy, oligomers such as a disilanebeing a dimer of the alkoxysilicate and a trisilane being a trimer ofthe alkoxysilicate, and the like are also considered as the silicaprecursors. Various compounds are commercially available as thehydrolyzable silane described above, and can be readily andinexpensively acquired, and it is easy to control a sol-gel reaction forforming a three-dimensional crosslinked body including a silicon-oxygenbond.

The acid or alkaline aqueous solution is an aqueous solution in which anacid or a base functioning as a catalyst for promoting a hydrolysisreaction of a silica precursor is dissolved in water as a solvent.Specific examples of the acid include acetic acid, hydrochloric acid,sulfuric acid, nitric acid, formic acid, oxalic acid and citric acid,and specific examples of the base include sodium hydroxide, potassiumhydroxide, aqueous ammonia, sodium carbonate, sodium hydrogen carbonate,amines such as trimethyl ammonium, ammonium hydroxides such astert-butyl ammonium hydroxide, and alkali metal alkoxides such as sodiummethoxide. Specific examples of the coexisting substance includepolyethylene oxide, polypropylene oxide, polyacrylic acid, blockcopolymers such as polyethylene oxide-polypropylene oxide blockcopolymers, cationic surfactants such as cetyltrimethylammoniumchloride, anionic surfactants such as sodium dodecyl sulfate, andnonionic surfactants such as polyoxyethylene alkyl ethers. Water is usedas a solvent, but an alcohol such as methanol or ethanol may be used.

In the gelation step, the precursor sol prepared in the sol preparationstep is injected into a gelation container, and gelled at a temperatureof, for example, about 40° C. at which sol-gel transition easilyproceeds. Here, in the precursor sol, a coexisting substance serving toinduce sol-gel transition and phase separation in parallel is added, andtherefore spinodal decomposition is induced to gradually form aco-continuous structure of a silica hydrogel (wet gel) phase and asolvent phase which has a three-dimensional continuous networkstructure.

In the gelation step, a polycondensation reaction of the wet gel slowlyprogresses to cause shrinkage of the gel even after the silica hydrogelphase is formed, and therefore, as a step subsequent to the gelationstep (post-gelation step), the co-continuous structure of the silicahydrogel phase and the solvent phase which is formed in the gelationstep is immersed in a basic aqueous solution such as aqueous ammonia,and subjected to a heating treatment in a pressurized container tofurther promote the hydrolysis reaction, the polycondensation reactionand a dissolution and reprecipitation reaction of the silica hydrogelphase, so that the skeleton structure of the silica hydrogel phase canbe further strengthened. The post-gelation step may be carried out asnecessary. The heating treatment is not necessarily required to beperformed in a pressurized container or a closed container, but since anammonia component or the like may be generated or volatilized byheating, it is preferable to perform the heating treatment in a closedcontainer or a container having pressure resistance.

As the dissolution and rep recipitation reaction of silica fineparticles forming the skeleton body of the silica hydrogel phaseproceeds, the diameter of pore formed in the skeleton body is increased.Further, when the dissolution and precipitation reaction is repeated inhydrothermal treatment, it is possible to perform control to furtherincrease the pore diameter. The control of the pore diameter can also beperformed by adding urea in the precursor sol besides a catalyst and acoexisting substance. Urea is hydrolyzed at a temperature of 60° C. orhigher to produce ammonia, and the pore diameter of the pore formed inthe skeleton body of the wet gel synthesized in the gelation step isincreased by the ammonia. Thus, it is possible to control the porediameter by adding urea. On the other hand, control of the structure andpore diameter of the through-hole is made possible by adjusting theamount of water or the silica precursor added to the precursor sol inthe sol preparation step, or the composition and addition amount of thecoexisting substance.

Subsequently, in the removal step, washing and drying, or only drying ofthe wet gel is performed to remove the solvent phase containingadditives, unreacted substances and the like. The space after removal ofthe solvent phase forms a through-hole. By washing, a surface tensionduring drying which is caused by additives, unreacted substances and thelike remaining in the solvent phase can be eliminated to suppressdistortion and cracking in the gel during drying. A washing liquid isdesirably a liquid such as an organic solvent or an aqueous solution. Aliquid in which an organic compound or an inorganic compound isdissolved can also be used. Further, even if a solution having a pHdifferent from the isoelectric point of the gel, such as an acid or analkali, is used as the washing liquid, additives and the like remainingin the gel can be easily removed. Specifically, various kinds of acidssuch as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoricacid, acetic acid, formic acid, carbonic acid, citric acid andphosphoric acid, and various kinds of bases such as sodium hydroxide,potassium hydroxide, ammonia, water-soluble amine, sodium carbonate andsodium hydrogen carbonate can be used. For drying the wet gel, naturaldrying may be adopted, and for eliminating distortion and cracksgenerated in drying of the wet gel, it is also preferable to adoptdrying that is performed after replacement of a solvent in the wet gelby a solvent having a surface tension lower than that of water, such asisopropanol, acetone, hexane and hydrofluorocarbon; drying by freezingand sublimation; supercritical drying that is performed in anon-surface-tension state after exchange of a solvent in the wet gelwith supercritical carbon dioxide; or the like.

Subsequently, the resulting dried gel can be sintered by firing toobtain silica glass. When the firing temperature is lower than the glasstransition temperature (about 1000° C.) of silica, silica glass is notformed.

By passing through the above sol preparation step, gelation step andremoval step, a monolithic porous body of dried silica gel or silicaglass of three-dimensional continuous network structure which has atwo-step hierarchical porous structure is obtained.

The granulation step is a step of crushing and granulating the massivemonolithic porous body obtained by passing through the above-mentionedsol preparation step, gelation step and removal step. The grindingtreatment in the granulation step may be performed manually, or using amortar or the like, or a crushing apparatus such as a ball mill. Whenthe dried gel obtained in the removing step is sintered, the granulationstep may be performed either before or after the sintering.

The granulated monolithic porous body after the granulation step isclassified by sieving with sieves having apertures of X μm and Yμm(D0≤X<Y≤D1), respectively, so that the granulated monolithic porous bodyis recovered as the granular porous body 1 with the particle diameter Dpfalling within a desired particle diameter range (D0 μm or more and 250μm or less). However, the lower limit D0 (μm) of the desired particlediameter range is 20 (μm) or twice the most frequent pore diameter ϕ1 m(μm) of the through-hole, whichever is larger. Further, the upper limitD1 (mm) of the desired particle diameter range is calculated from thelater-described relational expression according to a size of a reactionobject, a contact method in this reaction method, and a contact time.

In this embodiment, the pore diameter, the through-hole diameter and theparticle diameter can be each independently controlled as describedabove, and it is empirically known that when the most frequent porediameter ϕ1 m in the pore diameter distribution of through-holes 3 isequal to or more than 5 times of the most frequent pore diameter ϕ0 m ofpores 4, and the particle diameter Dp is equal to or more than 5 timesof the most frequent pore diameter ϕ1 m of through-holes 3, the skeletonbody 2 of each particle of the granular porous body 1 can retain athree-dimensional continuous network structure with a two-stephierarchical porous structure even after granulation. However, thisembodiment also encompasses particles having a particle diameter Dp thatis 2 to 5 times of the most frequent pore diameter ϕ1 m of thethrough-hole 3. This allows for the possibility that a small amount ofcrushed fragments that do not maintain a perfect three-dimensionalcontinuous network structure as generated in the granulation step existafter classification by sieving. Even when such fragments exist, themain distribution range of the particle diameter Dp is consistent withthe classification range of the sieve aperture: X μm or more and Y μm orless, and as described later, the influence of a granular porous bodyexisting in a small amount and having a small particle diameter Dp canbe ignored.

In addition, the through-hole diameter can be controlled within a rangeof 0.1 to 50 μm, i.e., a size that can be controlled in the basemonolithic porous body as a parent body. The upper limit is larger by afactor of 500 than the lower limit in through-hole diameter, but whenthe through-hole diameter is larger by a factor of 100 or more than themolecular size of the liquid, the liquid can be perfused at a sufficientspeed in the granular porous body. In addition, molecules in thesolution can be efficiently perfused to the pore surface due toconvection of solvent molecules.

The pore diameter can be freely controlled according to the molecularsize of the reaction object. In the case of a silica gel of single-poreparticles, the pore diameter can be controlled within a range of 2 to100 nm. In the granular porous body, for example, when the reactionobject substance is a metal ion, the appropriate pore diameter is about2 to 20 nm because the ion radius is 1 nm or less. In addition, in thecase of a molecule having a molecular weight of about several hundredsto 1000 and a molecular diameter of 1 to 5 nm, the pore diameter isdesirably 5 to 50 nm. In addition, in the case of a molecule having amolecular weight of more than 1000 and a molecular diameter of 5 nm ormore, the pore diameter is desirably 10 to 100 nm.

When the pore diameter is equal to the molecular diameter, the moleculecan enter the inside of the pore, and therefore the pore diameter isdesirably equal to or more than the molecular diameter. It is alsopossible to increase the curvature of the solid surface by making thepore diameter smaller than the molecular diameter and subject a part ofthe molecule to a chelate reaction. In addition, a pore having a sizelarger by a factor of 10 or more than the molecular diameter has areduced specific surface area, and hence reduced reaction efficiency,but the pore diameter can be made larger by a factor of 10 or more thanthe molecular size for, for example, suppressing a nonspecific reaction.In an example regarding a monolithic porous body, Patent Document 1above recommends that the pore diameter (center diameter) be 40 nm ormore and 70 nm or less as a preferred range with respect to the size(about 10 to 12 nm) of an antibody to be adsorbed. The pore diameter isabout 4 to 7 times of the size of the object to be adsorbed, and theratio of the size of the antibody and the pore diameter is consistentwith the ratio of the molecular diameter (1 to 5 nm) and the porediameter (5 to 50 nm) although there is a slight difference between themolecular sizes, and is also consistent with the relation of themolecular diameter (5 nm or more) and the pore diameter (10 to 100 nm).

This reaction method will now be described. This reaction method is areaction method for reacting a reaction object with a liquid containingthe reaction object being in contact with a granular porous body. Thereaction object is assumed to be a metal ion, a low-molecular-weightcompound having a molecular weight of 2000 or less, or a compound havinga molecular weight of 2000 or more and 1000000 or less. Particularly,the metal ion is assumed to be a transition metal ion that may be anoble metal ion. In addition, the reaction includes adsorption, ionexchange, complexation, catalytic reaction and the like, and thisreaction method can be used for these reactions.

Examples of the reaction include a method for removing impurities in aliquid, and a method for extracting only a target component from amixture in a liquid, and any of these methods makes use of interactionbetween the surface of an inorganic porous skeleton body of the granularporous body (including the surface of the inside of the pore) and themolecule of a reaction object. More specifically, it is possible toadsorb molecules by means of the acidity and charge of the surface ofthe skeleton body. It is also possible to introduce a functionalgroup-containing organic compound to the surface of the skeleton bodyvia physical interaction or a chemical bond, and use the granular porousbody as a functional granular porous body having an ion-exchangefunction etc. It is also possible to treat the granular porous bodyunder a reducing atmosphere with a hydrocarbon compound introduced tothe surface of the skeleton body, and use the granular porous body as acarbide surface, or to sinter the granular porous body under a reducingatmosphere, and use the granular porous body as a composite having aSi—C bond. It is also possible to subject the granular porous body to areduction treatment with a metal oxide introduced to the surface of theskeleton body, and use the granular porous body as a metal carrier.

For example, when a metal ion in a solution is reacted with and adsorbedto the granular porous body, the metal ion is adsorbed by undergoing acomplexation reaction with a functional group introduced to the surfaceof the skeleton body, and therefore by introducing a functional group tothe surface of the skeleton body, this reaction method can be used as amethod for efficiently removing a metal ion. Examples of the organicfunctional group having affinity specifically with a metal ion includefunctional groups having mercaptopropyl, thiocyanuric acid, and thioureaas mercapto groups and thiol groups containing a sulfur element, and theorganic functional group exhibits affinity with ions of Ag, Cd, Co, Cu,Fe, Hg, Ir, Ni, Os, Pb, Pd, Pt, Rh, Ru, Sc, Sn, Zn and the like.Examples of the functional group having a carboxylic acid group includeethylenediaminetriacetic acid, and the functional group exhibitsaffinity with ions of Ca, Cd, Co, Cr, Cs, Cu, Fe, Ir, La,lanthanoid-type elements, Li, Mg, Ni, Os, Pd, Rh, Ru, Sc, Sn, Zn and thelike. Examples of the functional group having a nitrogen element includeamine-based functional groups such as aminopropyl, aminoethylaminopropyl(diamine), aminoethylaminoethylaminopropyl (triamine) and imidazole, andthe functional group can exhibit affinity with Cd, Co, Cr, Cu, Fe, Ni,Os, Pb, Pd, Pt, Rh, Ru, W, Zn and the like. In addition, mention is madeof a phosphate group, a sulfate group, an ammonium group, a hydroxylgroup, a keto group, and a composite of these substituents.

Examples of the method for introducing a functional group include amethod for chemically fixing a functional group to the surface of theskeleton body via a covalent bond, and a method for physically fixing afunctional group via physical interaction such as ionic bonding orhydrophobic interaction. Examples of the method for chemicallyintroducing a functional group include a method in which a silanecoupling agent having a functional group is reacted to fix thefunctional group via a hydroxyl group on the surface of the skeletonbody (SiO₂).

Examples of the organosilane compound that can be used as a silanecoupling agent include trialkoxysilanes such as trimethoxysilane,triethoxysilane, triisopropoxysilane and trip henoxysilane,dialkoxysilanes such as methyldiethoxysilane, methyldimethoxysilane,ethyldiethoxysilane and ethyldimethoxysilane, monoalkoxysilanes such asdimethylethoxysilane and dimethylmethoxysilane, alkylchlorosilanes suchas octadecyltrichlorosilane, octadecylmethyldichlorosilane,octadecyldimethylchlorosilane, octadecylsilazane,octadecyltrimethoxysilane, octadecylmethyldimethoxysilane, octyl,trimethylchlorosilane (TMS), dimethyl-n-octylchlorosilane anddimethyl-n-octadecylchlorosilane (ODS), each of which has a substituentsuch as methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, hexadecyl,octadecyl, dodecyl, phenyl, vinyl, hydroxyl, ether, epoxy, aldehyde,carboxyl, ester, thionyl, thio or amino. Alkoxysilicates containing acrosslinking reaction rate controlling group substituent such as amonoalkyl, a dialkyl and a phenyltriethoxy, oligomers such as a disilanebeing a dimer of the alkoxysilicate and a trisilane being a trimer ofthe alkoxysilicate, and the like can also be used as silane couplingagents.

When the reaction object is a blue pigment, examples thereof includelow-molecular-weight compounds which are represented by a blue pigmentand have a molecular weight of 300 to 1000, such as Basic Blue 17(toluidine blue) having a molecular weight of 305.82, Brilliant Blue FCFhaving a molecular weight of 792.86, Indigo Carmine having a molecularweight of 466.36, and Coomassie Brilliant Blue having a molecular weightof 833.048. These blue pigments are adsorbed by chemical interactionwith the surface of the skeleton body (SiO₂). Here, direct chemicalinteraction with the surface of the skeleton body occurs, andintroduction of a functional group is unnecessary.

When the reaction object is a macromolecular compound contained in abrown sugar, examples of the macromolecular compound include flavonoidshaving a molecular weight of 1000 or less, melanins having a molecularweight of 150000 or more, chlorophyll, carotene, xanthophyll or the likehaving a molecular weight of 1000 or less, melanoidins having amolecular weight of 50000 or less, caramel having a molecular weight of25000 or less, and 6-carbon sugar decomposition products having amolecular weight of about 1000 to 5000, and these compounds have amolecular weight in a wide range of about 1000 to about 1000000. Inparticular, the brown sugar is rich in caramel (molecular weight ofabout 2000 to 25000) and melanoidins (molecular weight of about 3000 to50000). The macromolecular compound contained in the brown sugar isadsorbed through an ion-exchange reaction with a functional groupintroduced to the surface of the skeleton body. Examples of thefunctional group include a trimethylpropylammonium chloride group as aquaternary ammonium group. Other functional groups for ion exchangereaction mainly include a secondary or tertiary amine group, a sulfonategroup, a carboxylate group, and a phosphate group.

As described above, in this reaction method, a functional group isintroduced to the surface of the skeleton body according to the kind ofreaction object and reaction, and the functional group may be introducedto a monolithic porous body as a parent of the granular porous body,followed by passing through the granulation step to prepare a granularporous body to which the functional group is introduced. Alternatively,a monolithic porous body before introduction of the functional group maybe granulated to prepare a granular porous body, followed by introducingthe functional group.

Further, in this reaction method, any of a non-circulation-type columnflow method, a circulation-type column flow method, and a shaking methodis used as a method (contact method) in which a liquid containing areaction object is diffused into a granular porous body, and broughtinto contact with the granular porous body. In the non-circulation-typecolumn flow method in this reaction method, the liquid is caused tocontinuously pass into a column while the concentration of the reactionobject in the liquid is kept constant. In the circulation-type columnflow method in this reaction method, the post-reaction liquid releasedfrom an outlet of the column is returned to an inlet of the column, andcirculated. In the non-circulation-type and circulation-type column flowmethods in this reaction method, the liquid containing the reactionobject continuously passes through the column. In this respect, thisreaction method is different from liquid chromatography in which aliquid containing a mixture to be separated is caused to pass through acolumn, and temporarily adsorbed, and an eluent is continuously fed toseparate the mixture.

Next, performance in one example (Example 1) of this reaction methodusing the above-described granular porous body is compared withperformance in a comparative example using commercially availablesingle-pore particle silica gel. In this performance comparison, a metalion (copper ion) was reacted by a non-circulation-type column flowmethod, and a copper acetate aqueous solution (concentration: 4 mg/mL)was used as a liquid containing a copper ion. The solution was caused topass at a flow rate of 0.3 mL/minute through a main column filled with agranular porous body of Example 1 and a comparative example columnfilled with a silica gel of a comparative example, 0.3 mL of thesolution was recovered every one minute from each of outlets of thecolumns, a concentration ratio of the concentration of the solutioncollected at the column outlet (post-reaction concentration) and theinitial concentration before passing (post-reactionconcentration/initial concentration) was determined, and changes inconcentration ratio were compared.

The main column and the comparative example column are filled with thegranular porous body of Example 1 and the silica gel of the comparativeexample, respectively, in column containers each having an innerdiameter of 6 mm and a length of 20 mm, and both the columns have thesame column volume (equivalent to the volume of the granular porousbody) of about 0.56 mL. The space velocity SV (1/hour) is about 32.14.Mercaptopropyl is introduced as a functional group to each of thegranular porous body of Example 1 and the silica gel of the comparativeexample. The through-hole diameter and the pore diameter of the granularporous body of Example 1 are 0.1 μm and 2 nm, respectively, and the porediameter of the silica gel of the comparative example is 2 nm. Fivekinds of particle diameter ranges: 0.1 to 0.25 mm, 0.25 to 0.5 mm, 0.5to 1 mm, 1 to 2 mm and 2 to 4 mm were set as the particle diameter rangeof the granular porous body of Example 1, and four kinds of particlediameter ranges: 0.1 to 0.25 mm, 0.25 to 0.5 mm, 0.5 to 1 mm and 1 to 2mm were set as the particle diameter range of the silica gel of thecomparative example.

FIGS. 4(A) and 4(B) show a change in concentration ratio of thepost-reaction concentration and the initial concentration in Example 1and the comparative example, respectively. In both FIGS. 4(A) and 4(B),the ordinate represents the concentration ratio, and the abscissarepresents the number of measurements per minute. As is evident fromFIGS. 4(A) and 4(B), comparison between Example 1 and the comparativeexample in the same particle diameter range shows that the concentrationratio is lower and the leakage is smaller in Example 1 than in thecomparative example. Performance in the particle diameter range of 0.5to 1 mm in Example 1 and performance in the particle diameter range of0.1 to 0.25 mm in the comparative example are almost the same, and it isthus apparent that in Example 1, the particle diameter range can beincreased by a factor of about 5 times for the same space velocity SV.

This reaction method is characterized in that the particle diameterrange can be made larger as compared with the case where a silica gel ofsingle-pore particles is used as described above, and further, thismethod is characterized in that the upper limit D1 (mm) of the particlediameter range can be easily calculated from the later-describedrelational expression according to the size of a reaction object, thecontact method in this reaction method, and the contact time.

[Non-Circulation-Type Column Flow Method]

Next, the upper limit D1 (mm) when the contact method is anon-circulation-type column flow method is given by a relationalexpression with the contact time T (seconds) as a variable as shown inMathematical Formula 1 below. The function LN is a natural logarithm, Aiis a coefficient in the reaction object i, and Bi is a constant in thereaction object i. The contact time T (seconds) is a value obtained byconverting the reciprocal of the space velocity SV in terms of seconds,and is given by a value obtained by dividing the volume of the granularporous body, i.e., the volume of the column volume by the flow rate ofthe liquid (solution) containing the reaction object i.

D1=Ai×LN(T)+Bi  (Mathematical Formula 1)

In the following, coefficient Ai and constant Bi in Mathematical Formula1 above for each reaction object i are derived using a copper ion, apalladium ion, a blue pigment and a brown sugar as the reaction objecti. The deriving procedure will now be described.

In the same manner as in Example 1 in FIG. 4(A), the concentration ratioof the post-reaction concentration and the initial concentration ismeasured for a plurality of different space velocities SV for eachreaction object i. The column volume and the amount of the solutionsequentially collected from each column outlet are about 0.56 mL and 0.3mL, respectively, and are the same as in Example 1. The through-holediameter and the pore diameter of the granular porous body are 0.1 μmand 3 nm, respectively, and are the same as in Example 1. For theparticle diameter range, measurable one is appropriately selected fromthe five kinds of particle diameter ranges adopted in Example 1. Thespace velocity SV is adjusted by the flow rate of the solution.Therefore, the time interval at which 0.3 mL of the solution iscollected at the column outlet varies depending on the space velocitySV, but the number of measurements is invariably 1 to 10, and the totalamount of the solution to be measured is invariably 3 mL. However, forthe copper ion, there are two kinds of numbers of measurements: 10 (1 to10) and 5 (1 to 5) (the total amount of the solution is 1.5 mL) for thelater-described reason.

FIGS. 5(A) to 5(G) show the results of measuring a change inconcentration ratio of a post-reaction concentration and an initialconcentration for seven kinds of flow rates of the solution: 0.3mL/minute (SV=32), 0.6 mL/minute (SV=64), 1.5 mL/minute (SV=160), 3mL/minute (SV=321), 10 mL/minute (SV=1071), 20 mL/minute (SV=2142) and30 mL/minute (SV=3214) (Examples 1 to 7) where the reaction object i isa copper ion. The result in FIG. 5(A) is the same as in Example 1 inFIG. 4(A). The functional group introduced into the granular porousbody, the solution containing a copper ion, and the initialconcentration of the solution in Examples 2 to 7 are the same as inExample 1.

FIGS. 6(A) to 6(E) show the results of measuring a change inconcentration ratio of a post-reaction concentration and an initialconcentration for five kinds of flow rates of the solution: 0.6mL/minute (SV=64), 3 mL/minute (SV=321), 10 mL/minute (SV=1071), 20mL/minute (SV=2142) and 30 mL/minute (SV=3214) (Examples 8 to 12) wherethe reaction object i is a palladium ion. The functional groupintroduced into the granular porous body in each of Examples 8 to 12 isthe same as in Example 1. The solution containing a palladium ion is adinitrodiaminepalladium (II) solution, and has an initial concentrationof 165 μg/mL.

FIGS. 7(A) to 7(D) show the results of measuring a change inconcentration ratio of a post-reaction concentration and an initialconcentration for four kinds of flow rates of the solution: 0.3mL/minute (SV=32), 3 mL/minute (SV=321), 10 mL/minute (SV=1071) and 30mL/minute (SV=3214) (Examples 13 to 16) where the reaction object i is ablue pigment. A functional group is not introduced into the granularporous body in each of Examples 13 to 16. The solution containing a bluepigment is a Basic Blue 17 aqueous solution, and has an initialconcentration of 1 ppm.

FIGS. 8(A) to 8(D) show the results of measuring a change inconcentration ratio of a post-reaction concentration and an initialconcentration for four kinds of flow rates of the solution: 0.3mL/minute (SV=32), 3 mL/minute (SV=321), 10 mL/minute (SV=1071) and 30mL/minute (SV=3214) (Examples 17 to 20) where the reaction object i is abrown sugar. The solution containing a brown sugar is an aqueoussolution of a Hateruma-produced brown sugar (a mixture including a brownsubstance having a molecular weight of about 2000 to 1000000), and hasan initial concentration of 10 mg/mL. The functional group introducedinto the granular porous body in each of Examples 17 to 20 is atrimethylpropylammonium chloride group.

The contact times for the space velocities SV (SV=32, 64, 160, 321,1072, 2142 and 3214, each of which is an approximate value) adopted inthe above experiments are 112.5 seconds, 56.25 seconds, 22.5 seconds,11.215 seconds, 3.361 seconds, 1.681 seconds and 1.12 seconds,respectively.

FIGS. 5 to 8 show that irrespective of the reaction object i, the largerthe particle diameter range of the granular porous body, the higher theconcentration ratio, leading to an increase in ratio of a so called“leakage” in which the reaction object i in the solution passes througha column in an unreacted state. Therefore, the average of theconcentration ratios in a plurality of measurements indicates theleakage ratio of the whole solution passing through the column. FIGS. 5to 8 show that irrespective of the reaction object i, there is atendency that the larger the space velocity SV, i.e., the shorter thecontact time T, the higher the concentration ratio, leading to anincrease in leakage ratio, even in the same particle diameter range.

In addition, as is evident in the case of the copper ion, a reactionsite on the surface of the granular porous body (for example, afunctional group introduced in the case of a metal ion) is saturated tostart a breakthrough as the number of measurements increases, and thereis a tendency that the larger the particle diameter range of thegranular porous body, or the shorter the contact time, the earlier thestart of the breakthrough.

It is considered that in this reaction method, the leakage ratio shouldbe reduced to 50% or less for efficiently maintaining the reaction, andthus a relation between the upper limit D1 of the particle diameter Dpand the contact time T which is required for maintaining the leakageratio of 50% or less is derived for each reaction object i.Specifically, for each particle diameter range of each SV, the leakageratio is calculated from the results of measuring the concentrationratio as shown in FIGS. 5 to 8, on the basis of an average ofconcentration ratios in ten measurements (1 to 10), for eliminating theinfluence of measurement errors. In the case of a copper ion, theleakage ratio based on an average of concentration ratios in fivemeasurements (1 to 5) was calculated in addition to an average ofconcentration ratios in ten measurements (1 to 10) for allowing for theinfluence of the breakthrough.

From each SV for each reaction object i as calculated in the mannerdescribed above, and the leakage ratio in each particle diameter range,a particle diameter at which the leakage ratio at each SV (contact timeT) for each reaction object i is 50% is calculated. Specifically, amedian of the particle diameter range for the leakage ratio around aleakage ratio of 50% is linearly interpolated to determine a medianparticle diameter corresponding to a leakage ratio of 50%, and themedian particle diameter is multiplied by a ratio (1.33 in thisembodiment) of the upper limit and the median of the particle diameterrange to calculate the upper limit D1 (mm) of the particle diameter.From the upper limit D1 (mm) calculated in the manner described above,and the corresponding contact time T (seconds), the coefficient Ai andthe constant Bi in the relational expression in Mathematical Formula 1above are approximately calculated by a least squares error method.

The upper limit D1 (mm) derived for each reaction object i in the mannerdescribed above, the corresponding contact time T (seconds), and therelational expression are shown in each of the graphs in FIGS. 9(A) to9(E). In each of FIGS. 9(A) to 9(E), the ordinate represents the upperlimit D1 (linear expression), and the abscissa represents the contacttime T logarithmic expression). FIG. 9(A) shows results when thereaction object i is a copper ion and the number of measurements is 10.FIG. 9(B) shows results when the reaction object i is a copper ion andthe number of measurements is 5. FIG. 9(C) shows results when thereaction object i is a palladium ion. FIG. 9(D) shows results when thereaction object i is a blue pigment. FIG. 9(E) shows results when thereaction object i is a brown sugar.

The relational expressions in Mathematical Formula 1 above which arecalculated in FIGS. 9(A) to 9(E) are collectively shown in MathematicalFormulae 2 to 6 below.

copper ion (1 to 10 measurements)

D1=0.411×LN(T)+0.137  (Mathematical Formula 2)

copper ion (1 to 5 measurements)

D1=0.555×LN(T)+0.197  (Mathematical Formula 3)

palladium ion

D1=0.545×LN(T)+0.145  (Mathematical Formula 4)

blue pigment

D1=0.545×LN(T)+0.831  (Mathematical Formula 5)

brown sugar

D1=0.198×LN(T)+0.270  (Mathematical Formula 6)

Comparison between FIGS. 9(A) and 9(B) shows that even for the same ion(copper ion), the coefficients Ai and the constants Bi of the relationalexpressions in Mathematical Formulae 2 and 3 above, i.e., the gradientsand the intercepts (D1 axis) of the relational expressions inMathematical Formula 1 above which are linearly expressed on thesemi-logarithmic graph, are different between different numbers ofmeasurements. The difference in gradient and intercept may result fromthe influence of the breakthrough. On the other hand, comparison betweenFIGS. 9(B) and 9(C) shows that the gradients and the intercepts of therelational expressions in Mathematical Formulae 3 and 4 above are verysimilar between different metal ions although they are ions of the samemetals. That is, it is apparent that when the influence of thebreakthrough is small, a relation between the upper limit D1 and thecontact time T can be expressed by the same relational expression evenin different metal ions. Therefore, in this embodiment, the result witha measurement number of 5 in which the influence of breakthrough issmall is adopted in the case of a copper ion.

Comparison of FIGS. 9(B) and 9(C) with FIG. 9(D) shows that the reactionobjects i are different, i.e., metal ions and a blue pigment, and thekinds of reactions are different, i.e., a complexation reaction andadsorption by chemical interaction, but the gradients of the relationalexpressions in Mathematical Formulae 3 to 5 above are very similar. Thatis, it is apparent that the metal ion and the blue pigment show the samechange in upper limit D1 which is associated with a change in contacttime T. However, it is apparent that in the blue pigment, the interceptis larger by about 0.6 mm, and therefore the upper limit D1 of theparticle diameter range can be set larger by about 0.6 mm regardless ofthe contact time T.

FIG. 10 collectively shows the results in FIGS. 9(B) to 9(D). The brokenline (straight line) in FIG. 10 represents an overall relationalexpression in Mathematical Formula 1 above for the metal ions in whichthe result in five measurements for the copper ion and the result forthe palladium ion in FIGS. 9(B) and 9(C) are calculated in combination.The relational expression is shown in Mathematical Formula 7 below. FIG.10 shows that upper limits D1 at total 12 points for the copper ion andthe palladium ion are accurately approximated by the relationalexpression shown in Mathematical Formula 7 below. In addition, it isapparent that upper limits D1 at four points for the blue pigment areall located above the relational expression, and the relationalexpression can be used for setting the upper limit D1 for alow-molecular-weight compound, as the reaction object i, having amolecular weight of about 100 to 2000, such as a blue pigment. Forsetting the upper limit D1 for the low-molecular-weight compound, therelational expression shown in Mathematical Formula 5 may be used inplace of the relational expression shown in Mathematical Formula 7.

metal ion (copper ion+palladium ion)

D1=0.556×LN(T)+0.166  (Mathematical Formula 7)

Comparison between FIGS. 9(B) to 9(D) with FIG. 9(E) shows that when thereaction object i is a brown sugar, the gradient of the relationalexpression in Mathematical Formula 1 above is considerably differentfrom the gradients for other reaction objects i such as metal ions, andthe upper limit D1 for the brown sugar is clearly smaller than the upperlimits D1 for other reaction objects i at the same contact time.Accordingly, it is apparent that when the reaction object i is amacromolecular compound having a large molecular size, such as brownsugar, it is difficult to commonly use the relational expression formetal ions as shown in Mathematical Formula 7 above. Therefore, for acompound having a molecular weight of about 2000 to 1000000, such asbrown sugar, it is preferable to use the individual relationalexpression shown in Mathematical Formula 6.

In this embodiment, the initial concentration of each solution of thereaction object i is set to one kind of concentration, and this isbecause for the reason described below, it is considered that when theload capacity is 50% or less, the leakage ratio is constant irrespectiveof the initial concentration as long as there is no difference inparticle diameter range and contact time (space velocity SV). This hasalso been confirmed in preliminary experiments for this embodiment.

For example, when the reaction object i is a metal ion (Examples 1 to12), the fixed amount of the ligand (functional group) is almost equalto the retention volume of the metal ion. Here, the metal ion retentionamount refers to a reaction site on the surface of the particle of thegranular porous body. The fixed amount of the ligand is 0.8 mmol/g inthe case that a mercapto group is fixed. Since the bulk density is 0.3g/mL and the column volume is 0.56 mL, the metal ion retention volume is0.136 mmol. In the case of a copper ion, 3 mL of a copper acetate(molecular weight 181) aqueous solution with an initial concentration of4 mg/mL is caused to pass through the column in 1 to 10 measurements,and the loading amount of the metal ion is 0.066 mmol, i.e., 50% of themetal ion retention volume. In addition, when the loading amount of themetal ion exceeds 50% of the metal ion retention volume, the leakage(breakthrough) of the metal ion noticeably increases, and therefore theabove-described relational expression is not met.

When the concentration ratio is measured while the initial concentrationis decreased by, for example, diluting the solution to ½, ¼ . . . of theoriginal initial concentration, copper molecules do not fill thereaction site or effective specific surface area of the particlesurface, and thus the point at which the breakthrough starts to occur isdelayed, or as compared with the case of the original initialconcentration, the breakthrough is less noticeable, so that a flat curvelike the measurement result of the concentration ratio for palladium isobtained.

Conversely, when the concentration ratio is measured while the initialconcentration is increased by, for example, concentrating the solutionto 2 times, 4 times . . . of the original initial concentration, thetime during which copper molecules fill the reaction site or effectivespecific surface area of the particle surface is shortened, and thus thepoint at which the breakthrough starts to occur is advanced.

That is, when the column is continuously loaded with metal ions in sucha manner that the metal ion retention amount is 50% or less, the sameconcentration conforming to the relational expression with the contacttime T is obtained even if the concentration ratio is evaluated 50times, or even 100 times rather than 10 times in the case of dilutingthe solution, or the concentration ratio is evaluated 5 times ratherthan 10 times in the case of concentrating the solution.

In other reactions, for example adsorption by chemical interactions, itis impossible to infinitely adsorb reaction object molecules exceedingthe effective specific surface area of the granular porous bodyparticles, and it is considered that the reaction object molecules inthe liquid should not exceed the effective specific surface area or themaximum value for the reaction site, and the load capacity should be 50%or less.

The relational expression between the upper limit D1 of the particlediameter range of the granular porous body and the contact time T in thenon-circulation-type column flow method has been described above.

The through-hole diameter and the pore-diameter of the granular porousbody to be used in this reaction method will now be described on thebasis of experimental data. FIG. 11 shows results of evaluating theconcentration ratio where the reaction object is a copper ion in thesame manner as in Example 1 using this column with four kinds ofgranular porous bodies having a particle diameter range of 0.25 to 0.5mm, a through-hole diameter of 1 μm and pore diameters of 10 nm, 20 nm,30 nm and 40 nm, respectively (Example 21). The space velocity SV(solution flow rate) and the initial solution concentration are the sameas in Example 1. An average of the concentration ratios in 1 to 5measurements (leakage ratio) is calculated, and the result shows thatthe average is 6%, 11%, 41%, 59% in ascending order of the porediameters. When the pore diameter exceeds 20 nm, the leakage ratiorapidly increases, and therefore in the case where the reaction objectsubstance is a metal ion, the appropriate pore diameter is about 2 to 20nm as described above. When the pore diameter is 30 nm, the leakageratio is 50% or less, but when the space velocity SV is 32, the upperlimit D1 of the particle diameter range is about 2.7 mm, and thereforethe pore diameter is preferably 20 nm or less, more preferably 15 nm orless, still more preferably 10 nm or less in anticipation of an increasein particle diameter range.

FIGS. 12(A) to 12(C) show results of evaluating the concentration ratiowhere the reaction object is a copper ion in the same manner as inExample 1 using the main column with three kinds of granular porousbodies (Examples 22 to 24) in which at least one of the through-holediameter and the pore diameter of the granular porous body is changedfrom Example 1. In Example 22 shown in FIG. 12(A), the through holediameter and the pore diameter are 0.1 μm and 2 nm, respectively, andthe space velocity SV is 32. In Example 23 shown in FIG. 12(B), thethrough hole diameter and the pore diameter are 1 μm and 15 nm,respectively, and the space velocity SV is 32. In Example 24 shown inFIG. 12(C), the through hole diameter and the pore diameter are 50 μmand 10 nm, respectively, and the space velocity SV is 32. For theparticle diameter range in each of Examples 22 to 24, when an average ofthe concentration ratios in 1 to 5 measurements (leakage ratio) iscalculated and the upper limit of the particle diameter range at whichthe leakage ratio is 50% is determined in the same manner as incalculation of the coefficient Ai and the constant Bi, the result showsthat the averages are 2.28 mm, 1.61 mm and 2.35 mm, respectively, andeach not more than the upper limit D1 (=2.79) given by MathematicalFormula 7 from a contact time of 112.5 seconds at a space velocity SV of32, and thus this reaction method is applicable at a through-holediameter of 0.1 to 50 μm.

[Circulation-Type Column Flow Method and Shaking Method]

Next, the upper limit D1 (mm) of the particle diameter range in the casewhere the contact method is a circulation-type column flow method or ashaking method is given by the following relational expression formed ofa linear expression with the contact time T (seconds) as a variant asshown in Mathematical Formula 8 below. Ci is a coefficient of thefirst-order term in the reaction object i, and Di is a constant term inthe reaction object i. In the case of the circulation-type column flowmethod, the contact time T (seconds) is given by a value obtained bymultiplying a fluid flow time (seconds) of a liquid by a volume ratio Robtained by dividing a volume (column volume) of the granular porousbody by the volume of the liquid, and in the case of the shaking method,the contact time T (seconds) is given by a value obtained by multiplyingthe volume ratio R by the elapsed time after addition of the granularporous body in the liquid.

D1=Ci×T+Di  (Mathematical Formula 8)

Before the coefficient Ci and the constant Di in Mathematical Formula 8above are derived, first the relation between the “leakage ratio” in theshaking method and the particle diameter range, through-hole diameterand pore diameter of the granular porous body will be examined.

The shaking method is used as a method for collecting a noble metal froma solution containing the noble metal. In the shaking method used forcollecting a noble metal, a granular porous body as an adsorbent isadded in a solution containing a metal to be collected, and the mixtureis stirred or shaken to adsorb and remove the noble metal to becollected. In this embodiment, stirring is also considered as one modeof shaking.

As a solution containing palladium ions, 4 mL of adinitrodiaminepalladium (II) aqueous solution having an initialconcentration of 165 μg/mL as with Examples 8 to 12 was provided.Granular porous bodies (each in an amount of 10 mg) with 60 kinds ofcombinations of the particle diameter range, the through-hole diameterand the pore diameter as shown in FIG. 13 and commercially availablesingle-pore particle silica gels (each in an amount of 10 mg) ascomparative examples with four kinds of combinations of the particlediameter range and the pore diameter as shown in FIG. 13 were each addedin a container containing the aqueous solution, the mixture was stirredat a rotation speed of 33 rpm, and after elapse of 2 hours and afterelapse of 24 hours after the addition, a post-reaction palladium ionconcentration (post-reaction concentration) of the aqueous solution wasmeasured by an ultraviolet visible light absorptiometer. The 60 kinds ofthe particulate porous bodies and the four kinds of silica gels ascomparative examples all contain mercaptopropyl that is the samefunctional group as in Example 1 above.

In the 60 kinds of granular porous bodies, six kinds of particlediameter ranges: 0.106 to 0.25 mm, 0.25 to 0.5 mm, 0.5 to 1 mm, 1 to 2mm, 2 to 4 mm and 4 to 8 mm were set, five kinds of through-holediameters: 0.1 μm, 0.5 μm, 1 μm, 10 μm and 50 μm were set, and six kindsof pore diameters: 2 nm, 10 nm, 15 nm, 20 nm, 30 nm and 40 nm were set.In the four kinds of silica gels as comparative examples, six kinds ofparticle diameter ranges: 0.106 to 0.25 mm, 0.25 to 0.5 mm, 0.5 to 1 mmand 1 to 2 mm were set, and only one kind of pore diameter: 2 nm wasset. The combinations of the particle diameter range, the through-holediameter and the pore diameter are as shown in FIG. 13, and thedescription thereof will be omitted.

In FIG. 13, six kinds of particle diameter ranges are arranged in thelateral direction, and ten kinds of combinations of the through-holediameter and the pore diameter of the granular porous bodies and onekind of pore diameter of the silica gel in comparative examples arearranged in the longitudinal direction to form a 6×11 array, and in eachcell of the array, a concentration ratio obtained by dividing themeasured post-reaction concentration by the initial concentration isshown. Cells with a concentration ratio exceeding 50%, i.e., cells witha leakage ratio of 50% or more is shaded for the sake of convenience.

In the shaking method, it may be necessary to reduce the leakage ratioto 50% or less for efficiently maintaining the reaction as with thenon-circulation-type column flow method described above, and thus theleakage ratio is set to 50% or less as a practical range.

FIG. 13 shows that the larger the particle diameter range of thegranular porous body, the higher the concentration ratio and the largerthe leakage ratio. The shorter the elapsed time, the higher theconcentration ratio and the larger the leakage ratio even when thecombinations of the particle diameter range, through-hole diameter andpore diameter are the same. This tendency is the same as in the case ofthe non-circulation-type column flow method described above.

FIG. 13 shows that in a combination of the particle diameter range andthe pore diameter where the leakage ratio is 50% or less, a change inleakage ratio due to a change in through-hole diameter is lessnoticeable as compared with the particle diameter range and the porediameter. This tendency is the same as in the case where the contactmethod is a non-circulation-type column flow method.

From FIG. 13, there is a tendency that in the same particle diameterrange at the same elapsed time, the leakage ratio increases as the porediameter increases. This is because when the pore diameter increases,the specific surface area of the granular porous body decreases, leadingto deterioration of performance. When the pore diameter is 20 nm, theleakage ratio is 50% or less in a particle diameter range of 1 mm orless at an elapsed time of 24 hours, and when the pore diameter is 15nm, the leakage ratio is 50% or less in a particle diameter range of 4mm or less at an elapsed time of 24 hours, but when the particlediameter range increases, or the elapsed time is shortened, the leakageratio exceeds 50%. Therefore, depending on conditions, the upper limitof the pore diameter may be 20 nm, but is more preferably 15 nm, stillmore preferably 10 nm. This tendency is also the same as in the casewhere the contact method is a non-circulation-type column flow method.

FIG. 13 shows that the leakage ratios in all the four kinds of silicagels as comparative examples are 87% or more, and these silica gels arenot suitable for practical use in any of the particle diameter ranges.

Examples B and C will now be briefly described in whichaminoethylaminopropyl that is a functional group different from thefunctional group introduced to the surface of granular porous body usedin the example with 60 kinds of combinations as shown in FIG. 13(hereinafter, referred to as “Example A” for the sake of convenience) isintroduced to the surface of the granular porous body. In Example B, themetal ion as a reaction object was a palladium ion that is the same ionas in Example A, and in Example C, the metal ion as a reaction objectwas a ruthenium ion that is different from the metal ion in Example A.In Example B, 4 mL of a dinitrodiaminepalladium (II) aqueous solutionhaving an initial concentration of 165 μg/mL as in Example A wasprovided. In Example C, 4 mL of a ruthenium trichloride aqueous solutionhaving an initial concentration of 250 μg/mL was provided as a solutioncontaining a ruthenium ion. The granular porous bodies used in ExamplesB and C had a through-hole diameter of 1 μm and a pore diameter of 2 nm.In Examples B and C, a leakage ratio was measured in the same manner asin Example A.

FIG. 14 shows results of measuring the leakage ratio in the particlediameter ranges in Example B. FIG. 15 shows results of measuring theleakage ratio in the particle diameter ranges in Example C.

Comparison between combinations of the same through-hole diameter andpore diameter in FIGS. 14 and 13 at an elapsed time of 2 hour and at anelapsed time of 24 hours shows that both the combinations have a leakageratio of 50% or less in a particle diameter range of 2 mm or less at anelapsed time of 2 hours, both the combinations have a leakage ratio of50% or less in all the particle diameter ranges at an elapsed time of 24hours, and as a whole, there is no significant difference in performancedue to a difference in functional group although there is a differencebetween individual values for each particle diameter range.

Comparison between combinations in FIGS. 14 and 15 at an elapsed time of2 hour and at an elapsed time of 24 hours shows that both thecombinations have a leakage ratio of 50% or less in a particle diameterrange of 2 mm or less at an elapsed time of 2 hours, both thecombinations have a leakage ratio of 50% or less in all the particlediameter ranges at an elapsed time of 24 hours, and as a whole, there isno significant difference in performance due to a difference in metalion although there is a difference between individual values for eachparticle diameter range.

A procedure for deriving the coefficient Ci and the constant Di ofMathematical Formula 8 above in the shaking method using a palladium ionas the reaction object i will now be described.

In the derivation procedure, granular porous bodies with six kinds ofparticle diameter ranges as in Example A as the particle diameter range,and with three kinds of combinations (through-hole diameter/porediameter: 0.1 μm/2 nm, 0.5 μm/2 nm and 1 μm/2 nm) among six kinds ofcombinations in Example A were provided aside from Example A with 60kinds of combinations as shown in FIG. 13. Mercaptopropyl, which is afunctional group that is the same as in Example A, is introduced to thesurface of the granular porous body.

In addition, as solutions containing a palladium ion, total 24 kinds ofsamples: 18 kinds of dinitrodiaminepalladium (II) aqueous solutions(each in an amount of 4 mL) having an initial concentration of 165 μg/mLas in Example A, and six kinds of the aqueous solutions (each in anamount of 1 mL) were provided. Total 18 kinds of granular porous bodieswith the three kinds of through-hole diameters and six kinds of particlediameter ranges were added in an amount of 0.03 mL to 18 kinds of theaqueous solutions (each in an amount of 4 mL), respectively, andgranular porous bodies with a through-hole diameter of 1 μm and with sixkinds of particle diameter ranges were added in an amount of 0.01 mL to6 kinds of the aqueous solutions (each in an amount of 1 mL),respectively. The resulting mixtures were each stirred at a rotationspeed of 33 rpm.

At five measurement points: 10 minutes, 30 minutes, 60 minutes, 120minutes and 1440 minutes after addition of the granular porous bodies tototal 18 kinds of samples being the solutions (each in an amount of 4mL), a post-reaction palladium ion concentration (post-reactionconcentration) of the aqueous solution was measured by an ultravioletvisible light absorptiometer, and a leakage ratio was calculated from aconcentration ratio of the post-reaction concentration and the initialconcentration (post-reaction concentration/initial concentration).Further, at four measurement points: 2 minutes, 7 minutes, 12 minutesand 20 minutes after addition of the granular porous bodies to total sixkinds of samples being the solutions (each in an amount of 1 mL), apost-reaction palladium ion concentration (post-reaction concentration)of the aqueous solution was measured by an ultraviolet visible lightabsorptiometer, and a leakage ratio was calculated from a concentrationratio of the post-reaction concentration and the initial concentration(post-reaction concentration/initial concentration).

Next, for combinations of the same aqueous solution volume andthrough-hole diameter, a particle diameter at which the leakage ratio ateach of the five measurement points is 50% is calculated from theleakage ratio for each of the six kinds of particle diameter ranges.Specifically, a median of the particle diameter range for the leakageratio around a leakage ratio of 50% was linearly interpolated todetermine a median particle diameter corresponding to a leakage ratio of50%, and the median particle diameter was multiplied by a ratio (1.33 inthis embodiment) of the upper limit and the median of the particlediameter range to calculate the upper limit D1 (mm) of the particlediameter.

In the shaking method, the number of kinds of ratios of the volume ofthe solution and the volume of the granular porous body to be added isnot 1, and therefore it is not possible to simply compare cases wherethere is a difference in the ratio. For this reason, in this embodiment,a value obtained by multiplying the elapsed time by a volume ratioobtained by dividing the volume of the granular porous body by thevolume of the solution, and converting the resulting product in terms ofseconds is defined as the contact time T (seconds) of the relationalexpression in Mathematical Formula 8 above. Through correction with thevolume ratio, the elapsed time in the shaking method is converted into avalue corresponding to the contact time T (a value obtained byconverting the reciprocal of the space velocity SV in terms of seconds)in the non-circulation-type column flow method.

FIG. 16 is a view obtained by plotting the upper limit D1 of theparticle diameter calculated in the manner described above and thecorresponding contact time T (seconds). In FIG. 16, the ordinaterepresents the upper limit D1 (logarithmic expression), and the abscissarepresents the contact time T (logarithmic expression). In FIG. 16, thecalculation points are connected for each of four kinds of combinationsof the solution volume (4 mL and 1 mL) and the through hole diameter(0.1 μm, 0.5 μm and 1 μm) to show a polygonal line. Hereinafter, for thesake of convenience, four kinds of combinations of the solution volumeand the through-hole diameter (4 mL/0.1 μm, 4 mL/0.5 μm, 4 mL/1 μm and 1mL/1 μm) are referred to as Examples E1 to E4, respectively. In FIG. 16,results in the circulation-type column flow method are also shown, andthese results will be described later.

In the case of Examples E1 to E3 in which the volume of the solution was4 mL, there was a difference due to a difference in through-holediameter at an elapsed time of 24 hours (a contact time T of 648 secondsas corrected by the volume ratio). However, this difference is notnecessarily a difference caused by a difference in through-holediameter, but may be a measurement error caused by a long elapsed time.

FIG. 16 shows that at a contact time T of several hundred seconds orless, the upper limit D1 is distributed on substantially the samestraight line in each of Examples E1 to E4. In both Examples E3 and D4,the upper limit D1 is distributed on the same straight line, andtherefore it is apparent that correction in which the elapsed time ismultiplied by the volume ratio to determine the contact time T isappropriate. Thus, from the results shown in FIG. 16, it is apparentthat in the shaking method, the upper limit D1 of the particle diameterrange for attaining a leakage ratio of 50% or less is expressed by alinear function of the contact time T.

From the upper limit D1 and the corresponding contact time T in each ofExamples E1 to E4, which are plotted in FIG. 16, the coefficient Ci andthe constant Di of the linear function in Mathematical Formula 8 abovecan be approximately calculated by a least squares error method.

A procedure for deriving the coefficient Ci and the constant Di ofMathematical Formula 8 above in the case where the contact method is acirculation-type column flow method using a copper ion as the reactionobject i will now be described.

In the derivation procedure, granular porous bodies with six kinds ofparticle diameter ranges as in Example A as the particle diameter range,and with a through-hole diameter of 1 μm and a pore diameter of 2 nmwere provided. Mercaptopropyl, which is a functional group that is thesame as in Examples A and E1 to E4, is introduced to the surface of thegranular porous body. A column container having an inner diameter of 6mm and a length of 20 mm was filled with the above-mentioned granularporous body to obtain a main column to be used in the circulation-typecolumn flow method (referred to as Example F). The column volume is 0.56mL as in the case of the non-circulation-type column flow method.

In addition, 30 mL of a copper acetate aqueous solution (concentration:0.5 mg/mL) was provided as a solution containing a copper ion, andcontinuously circulated at a flow rate of 10 mL/minute in this column,i.e., the solution discharged from a column outlet was returned to acolumn inlet, and circulated. At four measurement points: 30 minutes, 60minutes, 120 minutes and 1440 minutes after the start of circulation, apost-reaction copper ion concentration (post-reaction concentration) ofthe aqueous solution was measured by an ultraviolet visible lightabsorptiometer, and a leakage ratio was calculated from a concentrationratio of the post-reaction concentration and the initial concentration(post-reaction concentration/initial concentration). FIG. 17 showsresults of measuring a concentration ratio at each measurement point.

Next, a particle diameter at which the leakage ratio at each of the fourmeasurement points is 50% is calculated from the leakage ratio for eachof the six kinds of particle diameter ranges. Specifically, a median ofthe particle diameter range for the leakage ratio around a leakage ratioof 50% was linearly interpolated to determine a median particle diametercorresponding to a leakage ratio of 50%, and the median particlediameter was multiplied by a ratio (1.33 in this embodiment) of theupper limit and the median of the particle diameter range to calculatethe upper limit D1 (mm) of the particle diameter.

In the case of the circulation-type column flow method, the solutiondischarged from the column outlet is returned to the column inlet, andsubjected to the reaction again unlike the case of thenon-circulation-type column flow method, and therefore, evidently it isproblematic that the contact time T (a value obtained by converting thereciprocal of the space speed SV in terms of seconds) adopted in thenon-circulation-type column flow method is used as it is. In addition,in the case of the circulation-type column flow method, the wholesolution and the whole of granular porous body are caused to come intocontact with each other by maintaining circulation unlike the case ofthe non-circulation-type column flow method, and therefore thecirculation-type column flow method has a behavior close to that in theshaking method. In addition, like the case of the shaking method, thenumber of kinds of ratios of the volume of the solution and the volumeof the granular porous body to be added is not 1, it is impossible tosimply compare cases where there is a difference in the ratio.

Accordingly, in this embodiment, like the case of the shaking method, avalue obtained by multiplying the elapsed time after the start of thepassage (fluid flow time of the solution) by a volume ratio obtained bydividing the volume of the granular porous body by the volume of thesolution, and converting the resulting product in terms of seconds isdefined as the contact time T (seconds) of the relational expression inMathematical Formula 8 above.

In FIG. 16, the contact time T (seconds) corresponding to the upperlimit D1 of the particle diameter calculated in the manner describedabove and results in the shaking method was plotted together with theresults in the shaking method in Examples E1 to E4 for facilitatingcomparison with results in the shaking method.

FIG. 16 shows that the results in the shaking method in Examples E1 toE4 and the results in the circulation-type column flow method in ExampleF are distributed together at almost the same position on the graph ofFIG. 16, and as in the case of Examples E1 to E4, the upper limit D1 isdistributed on almost the same straight line. That is, from the resultsshown in FIG. 16, it is apparent that in the circulation-type columnflow method, the upper limit D1 of the particle diameter range forattaining a leakage ratio of 50% or less is expressed by a linearfunction of the contact time T like the case of the shaking method.

From the upper limit D1 and the corresponding contact time T in each ofExamples E1 to E4 and F, which are plotted in FIG. 16, the coefficientCi and the constant Di of the linear function in Mathematical Formula 8above can be approximately calculated by a least squares error method.However, in this embodiment, the calculated coefficients Ci andconstants Di in Examples E1 to E4 and F are averaged, and the obtainedaverages were set to the coefficient Ci and the constant Di,respectively, of the linear function shown in Mathematical Formula 8above. The linear function derived in this manner is shown inMathematical Formula 9 below.

D1=0.0315×T+0.470  (Mathematical Formula 9)

For the shaking method and the circulation-type column flow method, acase where the reaction object i is a metal ion has been exclusivelydescribed, but in the non-circulation-type column flow method, there isa common tendency between the metal ion and the low-molecular-weightcompound having a molecular weight of 2000 or less in the relationshipbetween the upper limit D1 of the particle diameter range and thecontact time, and therefore in the case of the shaking method and thecirculation-type column flow method, there may be a similar commontendency.

OTHER EMBODIMENTS

Hereinafter, other embodiments of this reaction method and granularporous body will be described.

<1> In the embodiment described above, the inorganic compound that formsthe skeleton body 2 of the granular porous body 1 is assumed to besilica (silica gel or silica glass), but the inorganic compound is notlimited to silica, and oxide porous bodies containing a typical metalelement such as aluminum, phosphorus, germanium or tin, or a transitionmetal element such as titanium, zirconium, vanadium, chromium, iron,cobalt, nickel, palladium, platinum, copper, silver, gold or zinc canalso be used. In addition, inorganic oxide porous bodies including acomposite containing an alkali metal element such as lithium or sodium,an alkaline earth metal element such as magnesium or calcium, or alanthanum-based element such as lanthanum and cerium can also be used.

An example of a method for synthesizing a titania monolithic porous bodybefore granulation where the skeleton body 2 of the granular porous body1 is titania (TiO₂) will be briefly described.

To a mixed solution of 2.5 mL of 1-propanol containing 0.4 g ofpolyethylene glycol (average molecular weight: 10000) and 2.5 mL ofethyl acetoacetate is added 5.0 mL of tetra-n-propyl titanate, 1.0 mL ofa 1 mol/L ammonium nitrate aqueous solution is then added with stirringto obtain a homogeneous solution, and the solution is transferred into asealed container, and left standing at 40° C. for 1 day to gel thesolution. The resulting gel is immersed in a mixed solvent of water andethanol for 1 day to be washed, and is then naturally dried, andsintered at 500° C. for 5 hours to obtain a titania monolithic porousbody.

When the inorganic compound that forms the skeleton body 2 is titania,titania is superior in acid resistance and alkali resistance to silica,and while silica is dissolved in an aqueous solution having a pH of 2 orless or a pH of 11 or more, titania can be used without being dissolvedin such an aqueous solution.

<2> In the embodiment described above, examples are described whilespecific values (quantity, temperature, time and so on) are clearlyshown regarding the method for synthesizing a monolithic porous body,but the numerical conditions in the synthesis method are not limited tothose shown in the examples.

<3> In the embodiment described above, since the granular porous body 1has a two-step hierarchical porous structure including through-holes 3and pores 4, the monolithic porous body in the process of preparing thegranular porous body 1 is assumed to have a similar two-stephierarchical porous structure. However, the monolithic porous bodybefore granulation may have a three-step hierarchical porous structurehaving holes with a pore diameter larger than that of the through-hole3, in addition to through-holes 3 and pores 4. Here, at the time whenthe monolithic porous body is ground and granulated to prepare thegranular porous body 1, the skeleton body 2 is ground along the holes,and therefore in the process of forming the holes, the diameter of theskeleton body 2 surrounded by the pores are made uniform to some degree,so that the particle diameter Dp of the ground granular porous body 1can be efficiently made to fall within a certain range.

<4> In the embodiment described above, as the reaction object ispecifically used in measurement of a leakage ratio, a copper ion, apalladium ion and a ruthenium ion are employed in the case of the metalion, Basic Blue 17 is employed in the case of the blue pigment, and aHateruma-produced brown sugar is employed in the case of the brownsugar, but the metal ion, the low-molecular-weight compound having amolecular weight of 2000 or less, and the compound having a molecularweight of 2000 or more and 1000000 or less as the reaction object i arenot limited thereto.

INDUSTRIAL APPLICABILITY

This reaction method, granular porous body and column according to thepresent invention can be used in various reaction methods for reacting areaction object such as a metal ion with a liquid containing thereaction object being in contact with the granular porous body, such asadsorption, ion exchange, complexation and catalytic reaction, andmethods for bringing a filter, an adsorbent, a reaction material, asolid phase catalyst or the like into contact with a liquid,particularly methods for adsorbing a metal in a solution and collectingmaterials.

DESCRIPTION OF SYMBOLS

-   -   1 Granular porous body    -   2 Skeleton body    -   3 Through-hole    -   4 Pore

1. A reaction method for reacting a reaction object with a liquidcontaining the reaction object being in contact with a granular porousbody, wherein the reaction object is a metal ion, or alow-molecular-weight compound having a molecular weight of 2000 or less,the method includes a column flow method in which the liquid is causedto pass through a column filled with the granular porous body, so thatthe liquid is diffused in the granular porous body, or a shaking methodin which the granular porous body is dispersively added in the liquid,and the liquid and the granular porous body are shaken to diffuse theliquid in the granular porous body, the granular porous body includes askeleton body including an inorganic compound having a three-dimensionalcontinuous network structure, and has a two-step hierarchical porousstructure including through-holes formed in voids in the skeleton body,and pores extending from a surface to an inside of the skeleton body anddispersively formed on the surface, a most frequent pore diameter in apore diameter distribution of the pores is within a range of 2 nm ormore and 20 nm or less when the reaction object is a metal ion, and themost frequent pore diameter of the pores is within a range of 5 nm ormore and 50 nm or less when the reaction object is thelow-molecular-weight compound, a most frequent pore diameter in a porediameter distribution of the through-holes is equal to or more than 5times of the most frequent pore diameter of the pores, and within arange of 0.1 μm or more and 50 μm or less, a particle diameter of thegranular porous body is equal to or more than 2 times of the mostfrequent pore diameter of the through-holes, and within a range of 20 μmor more and not more than an upper limit D (mm) defined depending on acontact time T (seconds) between the liquid and the granular porousbody, the upper limit D is given by:D=0.556×LN(T)+0.166 where the function LN is a natural logarithm in acase of the column flow method in a non-circulation type in which theliquid is caused to continuously pass through the column while aconcentration of the reaction object in the liquid is kept constant; orD=0.0315×T+0.470 in a case of the column flow method in a circulationtype, in which the liquid after the reaction is returned to the column,and continuously circulated, and the shaking method, and the contacttime T (seconds) is given by: a value obtained by dividing a volume (m³)of the granular porous body by a flow rate (m³/second) of the liquid inthe case of the column flow method in a non-circulation type; a valueobtained by multiplying a fluid flow time (seconds) of the liquid by avolume ratio obtained by dividing the volume of the granular porous bodyby a volume of the liquid in the case of the column flow method in acirculation type; or a value obtained by multiplying the volume ratio byan elapsed time (seconds) after addition of the granular porous body inthe liquid in the case of the shaking method.
 2. The reaction methodaccording to claim 1, wherein the reaction object is a metal ion, and afunctional group having affinity with the metal ion is chemicallymodified on the surface of the granular porous body.
 3. The reactionmethod according to claim 2, wherein the metal ion is adsorbed to thesurface of the granular porous body by undergoing a complexationreaction with the functional group.
 4. A reaction method for reacting areaction object with a liquid containing the reaction object being incontact with a granular porous body, wherein the reaction object is acompound having a molecular weight of 2000 or more and 1000000 or less,the method includes a non-circulation-type column flow method in whichwhile a concentration of the reaction object in the liquid is keptconstant, the liquid is caused to continuously pass through a columnfilled with the granular porous body, so that the liquid is diffused inthe granular porous body, the granular porous body includes a skeletonbody including an inorganic compound having a three-dimensionalcontinuous network structure, and has a two-step hierarchical porousstructure including through-holes formed in voids in the skeleton body,and pores extending from a surface to an inside of the skeleton body anddispersively formed on the surface, a most frequent pore diameter in apore diameter distribution of the pores is within a range of 10 nm ormore and 100 nm or less, a most frequent pore diameter in a porediameter distribution of the through-holes is equal to or more than 5times of the most frequent pore diameter of the pores, and within arange of 0.1 μm or more and 50 μm or less, a particle diameter of thegranular porous body is equal to or more than 2 times of the mostfrequent pore diameter of the through-holes, and within a range of 20 μmor more and not more than an upper limit D (mm) determined depending ona contact time T (seconds) between the liquid and the granular porousbody, the upper limit D is given by:D=0.198×LN(T)+0.270 where the function LN is a natural logarithm, andthe contact time T is given by a value obtained by dividing a volume(m³) of the granular porous body by a flow rate (m³/second) of theliquid.
 5. The reaction method according to claim 4, wherein afunctional group having affinity with the reaction object is chemicallymodified on the surface of the granular porous body.
 6. The reactionmethod according to claim 1, wherein the granular porous body isobtained by grinding and granulating a massive porous body prepared by asol-gel method, the massive porous body includes a skeleton bodyincluding the inorganic compound having a three-dimensional continuousnetwork structure, and has a two-step hierarchical porous structureincluding through-holes formed in voids in the skeleton body, and poresextending from a surface to an inside of the skeleton body anddispersively formed on the surface, a most frequent pore diameter in apore diameter distribution of the pores of the massive porous body iswithin a range identical to the range of the most frequent pore diameterin the pore diameter distribution of the pores of the granular porousbody, and a most frequent pore diameter in a pore diameter distributionof the through-holes of the massive porous body is within a rangeidentical to the range of the most frequent pore diameter in the porediameter distribution of the through-holes of the granular porous body.7. The reaction method according to claim 1, wherein the inorganiccompound is silica or titania.
 8. A granular porous body used forreaction with a metal ion, wherein the granular porous body includes askeleton body including an inorganic compound having a three-dimensionalcontinuous network structure, and has a two-step hierarchical porousstructure including through-holes formed in voids in the skeleton body,and pores extending from a surface to an inside of the skeleton body anddispersively formed on the surface, a most frequent pore diameter in apore diameter distribution of the pores is within a range of 2 nm ormore and 20 nm or less, a most frequent pore diameter in a pore diameterdistribution of the through-holes is equal to or more than 5 times ofthe most frequent pore diameter of the pores, and within a range of 0.1μm or more and 50 μm or less, a particle diameter of the granular porousbody is equal to or more than 2 times of the most frequent pore diameterof the through-holes, and within a range of 20 μm or more and 4 mm orless, and a functional group having affinity with the metal ion ischemically modified on a surface of the granular porous body.
 9. Thegranular porous body according to claim 8, wherein the functional grouphas a function of adsorbing the metal ion to the surface of the granularporous body by undergoing a complexation reaction with the metal ion.10. The granular porous body according to claim 8, wherein the granularporous body is obtained by grinding and granulating a massive porousbody prepared by a sol-gel method, the massive porous body includes askeleton body including the inorganic compound having athree-dimensional continuous network structure, and has a two-stephierarchical porous structure including through-holes formed in voids inthe skeleton body, and pores extending from a surface to an inside ofthe skeleton body and dispersively formed on the surface, a mostfrequent pore diameter in a pore diameter distribution of the pores ofthe massive porous body is within a range identical to the range of themost frequent pore diameter in the pore diameter distribution of thepores of the granular porous body, and a most frequent pore diameter ina pore diameter distribution of the through-holes of the massive porousbody is within a range identical to the range of the most frequent porediameter in the pore diameter distribution of the through-holes of thegranular porous body.
 11. The granular porous body according to claim 8,wherein the inorganic compound is silica or titania.
 12. A column usedfor reaction with a metal ion, wherein a column container is filled withthe granular porous body according to claim
 8. 13. The column accordingto claim 12, wherein a particle diameter of the granular porous body isnot more than an upper limit D (mm) determined depending on a contacttime T (seconds) between a liquid containing the metal ion and thegranular porous body, the upper limit D is given by:D=0.556×LN(T)+0.166 where the function LN is a natural logarithm, andthe contact time T is given by a value obtained by dividing a volume(m³) of the granular porous body by a flow rate (m³/second) of theliquid, in a case where passage of the liquid is non-circulation-typepassage, and the upper limit D is given by:D=0.0315×T+0.470, the contact time T is given by a value obtained bymultiplying a fluid flow time (seconds) of the liquid by a volume ratioobtained by dividing the volume of the granular porous body by a volumeof the liquid, in a case where passage of the liquid is circulation-typepassage.
 14. The reaction method according to claim 4, wherein thegranular porous body is obtained by grinding and granulating a massiveporous body prepared by a sol-gel method, the massive porous bodyincludes a skeleton body including the inorganic compound having athree-dimensional continuous network structure, and has a two-stephierarchical porous structure including through-holes formed in voids inthe skeleton body, and pores extending from a surface to an inside ofthe skeleton body and dispersively formed on the surface, a mostfrequent pore diameter in a pore diameter distribution of the pores ofthe massive porous body is within a range identical to the range of themost frequent pore diameter in the pore diameter distribution of thepores of the granular porous body, and a most frequent pore diameter ina pore diameter distribution of the through-holes of the massive porousbody is within a range identical to the range of the most frequent porediameter in the pore diameter distribution of the through-holes of thegranular porous body.
 15. The reaction method according to claim 4,wherein the inorganic compound is silica or titania.